Bone conduction audiphone



Nov. 11, 1941. w. A. zARTH BONE CONDUCTION AUDIPHONE Filed April 8, 1939 f", 3231"II www a. Zarza?,

Patented Nov. 11, 1941 UNlEo STATES BONE coNDUcrIoN AUDIPHONE William A. rzarih, Jamaica, N. Y., assigner to Dictograph Products Company, Inc., New York, N. Y., a corporation of Delaware Application April s, 1939, Serial No. 266,757 s claims. (cl. 179-1077) This'invention relates to audiphones, and has particular reference to bone conduction audiphones having a vibratory member adapted to be placed in operative connection with the bone structure of the user for transmitting therethrough to the inner ear the audible sounds conduction audiphones, the vibratory member of l the electromagnetic means is supported by a headband or the like, with the relatively massive part of the electromagnetic means floatingly mounted with respect thereto, so that while the vibrations across the air gap are normal to the bone surface, they are applied indirectly thereto, being reactive vibrations of the vibratory member relatively to the said massivevpart because of the high relative inertia of the latter. An example of this class of audiphone is illustrated in Patent No. 2,148,024, issued-February 21, 1939, to Henry Koch While both classes of audiphones have proven generally satisfactory, there are certain objections to each. For example, with the r'st or direct-acting class, the free vibrations of the reed connected to the vibratory member are liable to be suppressed to a certain degree by In accordance with the present invention, a

bone conduction audiphone is providedl which Aembody their disadvantages. In a preferred emadapted to be placed in operative connection with the bone structure of the user, carries an electromagnetic means having a vibratory element which vibrates independently of the member and in a direction generally parallel to the surface of the bone which the member engages, intsead of normal thereto, as in the ,case of both classes of prior audiphones, whereby the vibrations of the member are not suppressed b y its contact with the bone and the inertia of the parts is not relied von to provide the requisite vibration, so thatless power is required,

More particularly, the audiphone of this in-- vention comprises a' Contact plate serving as the vibratory member, to which is secured one side of a generally ring-shaped core slotted transversely at a point substantially opposite its point of connection with the member to form an air gap. The core is semi-flexible, so that the poles forming the air gap are movable relatively to each other in response to changes in the magnetic ux across thegap induced by voice currents traversing windings associated therewith. Inasmuch as this vibration is generally parallel to the vibratory member and engaged bone surface, the component thereof is transmitted through the connection between the core and the vibratory member, so that the latter vibrates with minute but powerful vibrations, which are transmitted through the bone to the inner ear of the user.` A cover mounted on the contact `plate or vibratory member encloses the electromagnetic means so that theV entire unit vibrates bodily and may be resiliently supported by a headband or the-like in the usual way. A

In a modified'form of the invention an armature, a second coreextends normally to the-face plate or vibratory member, with itsl end lying in the air gap of the core, thereby forming a generally E-shaped structure having two flux paths `and two air gaps, each of the two flux paths so formed being shorter than the ux path of the flrst form,

It will be seen that the bone conduction vaudiphoneof this invention is a very simple and effective device for securing efficient vibrations of the bone-without expenditure of a large amount of power and without variation of the airgap, due lto pressure of the receiver on the bone. Because the inertia of the electromagnetic means is not utilized during the' operation of the new device, the mass thereof need not be great but only sulcient to provide an eiicient ux path to secure the vibrations necessary for audible and inbodiment of the invention, the vibratory member telligible audition.

ing drawing, in which:

FigureA 1 is a longitudinal section through a preferred embodiment of the bone conduction as iron, soft steel, aluminum-nickel alloy, cobaltalong the line 3- 3 of Fig. 1;

vFig. 4 illustrates a modication of the formaudiphoneof this invention, as seen along the line I'-I of Fig. 2;

Fig. 2 is a plan view thereof with the cover removed;

battery 25, as shown in Fig. 5, and preferably a suitable amplifier, not shown. Two contact prongs 26 in' this circuit are adapted to be removably received in corresponding holes 21 in 5 the cover II, shown in Fig. 1. Extending into each of thesel holes 2l isa contact member 28 electrically connected by coil spring 29 to a connecting strip 30 on which .the spring 29 rests. There are two such assemblies and corresponding Fig, 3 is a transverse section thereof -as seen 10 connector strips 30, the latter being preferably shown in Figs. 1 to 3, inclusive; and

Fig. 5 illustrates the manner of supporting the audiphone on a headband and the manner of connecting it in a microphone circuit,

' Referring to Fig. l1 of the drawing, numeral I0 designates the contact plate, preferably of nonmetallic material. such as synthetic resin, having a relatively substantial area on the order of one square inch, and being relatively at for placeinlaid flush with the inner surface of the cont tact plate I and having their ends 3| extending upwardly adjacent the coils 22 and/or 23, depending upon whether they are connected in l parallel or in series. Light fllamentary conductors 32 leading to and from the coils 22 and 23 are soldered or otherwise electrically connected to the ends of conductingstrips 30. Accordingly, when the connector prongs 26 are inserted in the /holes 21 they connect the coils22 and 23 into the circuit of microphone 24.

ment in operative connection with the bone struc-'""""""'As shown in Figs. 3 and 5, a headband 33 havture of the user to serve as the vibratoryioember which transmits vibrations to"the inner ear through the bone structur of the user. The

'contact plate I0 may serve as a wally of a casing,

may be integral as'shownin Figs. 1 and 3, or may Y l 35 the two arms I6 and I'I in effect pivot about the be a washer or the like, as, shown in Fig-4. Mounted on this boss or washer I3 and rigidly secured by one side to plate I3 by tap screws vI4 is a ring-shaped core I5 of magnetically-permeable or permanently magnetizable material, such iron alloy, or the like. The co're I5 is not a completely closed ring but has a narrow transverse slot at a point substantially opposite the boss I3,

so that the core is generally C-shaped, having two arms I6 and II extending laterally to either piece of relatively wide flat stock, so that it is 'inherently semi-nexible in a vertical plane, permitting relative movement between the pole pieces .I8 across the air gap 20 in-a direction generally parallel to thelsurface of the contact plate I0. The exibility of the core I5 about the boss I3 may be augmented by saw-cutting the core transversely as indicated at 2I in Fig. 1. By reason of their bow shape, the arms I6 and I'I, though extending only a short distance from plate III, produce the vibratory effect on base I0 of long straight armsupstanding from the base.

Mounted on the arms I6 and I'I ofthe core I5 are the voice coils 22 and 23, respectively. These coils 22 and 23 are oppositely wound and connected either in parallel or in series in such a way that, when traversed by voice currents, the flur across the air gap 20 is varied to cause relative vibration between the arms I6 and I1 of the 70 core I5 in a direction substantially parallel to the surface of the contact plate or vibratory ing a fork 34, whose pivot pins 35 are connected to the sides of the cover II adjacent the air gap 20, may be used for holding the contact plate or vibratory member I3 in operative. connection with the mastoid eminence of the user, or some other part of his bone structure.

In operation of the bone conduction'laudiphone illustrated in Figs. 1 to 3, inclusive, the

general center point of the core I5 adjacent the boss I3 so that the vibration between the -poles I8 and I9 across the air gap. 20 is in a direction generally parallel to the surface of the contact 40 plate or vibratory member I0. Since the amplitude of this vibration is small, the component thereof, which is the useful vibration transmitted to the contact plate of vibratory member I0, is so minute that it is practically unmeasureable.

Nevertheless, the vibrations are powerful, and

are readily heard and intelligible to deafened persons, it appearing that the comparatively large amplitudes of vibrations of the two classes of prior bone conduction audiphones being unnecessary to good bone audition.

In the modification illustrated in Fig. 4, the core I5' is constituted of several parts instead of being integral, as in Fig. 1, although the core of Fig. 1 may also'be made up of several parts. Two

L-shaped arms I6' and I'I' are each secured at one of their ends to a magnetically permeable spring 36 securedv at its center over spacing washer I3' to contact plate Ill' by screws I4'.

' The other ends of the arms I6 and I'I. are spaced from opposite sides of a center core 3'I also mounted on spring 36 and forming with the poles I8' and I9 of respective arms I6' and I1' the two respective magnetic gaps 38 and 33. The entire core is accordingly generally E-shaped, as

5 shown in Fig. 4.

In the modication of Fig. 4, but one voice coil 40 is employed and is mounted on the second core 3l, although if desired two voice coils may be mounted on the two arms of the core I5' as shown in Fig. 1, and further, if desired, there may be three such coils, one on the second core 3,1, and two on the core I5', depending upon requirements.

In the arrangement of Fig. 4, the' two flux paths, one traversing arm I6', air gap 38, and center core 31, and the other traversing arm I1', air gap 39 and center core 31, are each shorter than the flux path traversing core I5 in Fig. 1 for equal flux density per unit of pole surface area. Also, the air gaps 38 and 39 may be made smaller than air gap in Fig. 1 since, for the same amplitude of vibration of the arms I6, Hand I6', I1', the vibration is divided between the two air gaps in the form of Fig. 4. The operation of the form of Fig. 4 will be readily understood from the description of the operation of Fig. 1, are essentially the same.

While certain preferred embodiments of this invention have been illustrated and described,A

herein, it is to be understood that the invention is not limited thereby but is susceptible of variations in form and detail within the scope of the appended claims. For example, the cores I5 and I5 may be any shape with the speech coils mounted on the horizontal arms instead of the vertical arms, so long as the general direction of the vibration across the air gap is substantially parallel to the contact plate surface engaging the bone.

I claim:

1. In a bone conduction audiphone, the combination of a vibratory member having a relatively fiat surface adapted to be operatively connected with the bone structure of the user, a pair of elesince they gap affording limited relative vibration between said parts substantially parallel to the surface of said member, and a winding associated with said elements for varying the magnetic iiux traversing said elements and said air gap in response to voice currents, whereby the component of the commensurate relative vibration between said elements due to their leverage about said mounting is transmitted through at least one .of said elements, the member and the connected bone structure to the inner ear of the user.

2. In a bone conduction audiphone, the combination of a vibratory member having a relatively fiat contact surface, electromagnetic means comprising a core attached to, said member and a winding thereon, said core having arms extending a substantial distance laterally to either side of the point of attachment with their ends turned inwardly to form a gap substantially opposite 3. In a bone conduction audiphone, the com` bination of al vibratory member having a substantially iiat contact surface, electromagnetic means comprising a core attached to said member and a winding thereon, said core having arms extending laterally vin. opposite directions a substantial distance and then upwardly from said member with their free ends turned inwardly to form a gap across which the said ends of said arms relatively vibrate in a direction substantially parallel to said surface, and44 means for supporting said member with its said surface in operative connection with the bone structure of vthe user for transmitting the component of the said rst portion in spaced relation with their free ends turned inwardly to form a gap across which the said ends of said arms relatively vibrate in a direction substantially parallel to said surface, said core having a transverse dimension parallel to said surface which is at least as great as its dimension normal to said surface, and means for supporting said member with its said surface in operative connection with the bone structure of the user for transmitting the component of the said vibration through said core, the said point of attachment, said member, and said bone structure to the inner ear.

5. In a bone conduction audiphone, the com bination of a housing including a-substantially flat contact plate adapted to be operatively connected with the surface of the bone structure of the user, electromagnetic means comprising a core and a winding thereon, said core having arms spaced apart a substantial distance and connected together at one end and secured at that end to said plate with their free ends spaced from said one end, extending substantially parallel to said plate and forming a gap traversed by flux in a direction substantially parallel to said plate, the association of said arms aiording'limited relative vibration between their free ends in response to variations in magnetic flux across said gap induced by voice currents traversing said winding, and means for supporting said plate in operative connection with said bone structure for transmitting the component of said vibration therethrough to the inner ear.

6. In' a bone conduction audiphone, the combination of a vibratory member adapted to be operatively connected with the surface of the bone structure of the user, electromagnetic means comprising a core and a winding thereon, said core having a flattened C-shape and being secured to said member at its flattened side opposite the gap to form two opposite arms connected for relative vibration` across said gzip in response to variationszininagnetic flux induced in said arms by voice currents traversing said Winding, whereby the rcomponent of said vibration is transmitted` through said member and connected bone structure to the inner ear.

'7. In a bone conduction audiphone, the combination of a vibratory member adapted to be operatively connected with the surface vof the bone structure of the user, electromagnetic means having a flattened C-shaped core secured to said member at its flattened side substantially opposite thegap to form two opposite arms connected for limited relative vibration across saidl gap,. and windings on the arms of said core arranged for varying the magnetic ux across said gap when energized by voice currents to effect said relative vibration between the members,

substantially opposite the gap in the core to form 10 two opposite arms for 1imited relative vibration across said gap, and a winding on each arm, said windings being arranged to vary the magnetic flux across said gap when energized by voice currents to eiect relative vibration between tlie members about said means, whereby the component of said vibration is transmitted through the member and connected bone to the vinner ear. 

